The present invention relates to the field of filters and filter materials for the removal of microorganisms and processes thereof, and, more particularly, to the field of filters and filter materials comprising particles coated with an activated lignosulfonate.
Water may contain many different kinds of contaminants including, for example, particulates, harmful chemicals, and microbiological organisms, such as bacteria, parasites, protozoa and viruses. In a variety of circumstances, these contaminants must be removed before the water can be used. For example, in many medical applications and in the manufacture of certain electronic components, extremely pure water is required. As a more common example, any harmful contaminants must be removed from water before it is potable, i.e., fit to consume. Despite modern water purification means, the general population is at risk, and in particular infants and persons with compromised immune systems are at considerable risk.
In the U.S. and other developed countries, municipally treated water typically includes one or more of the following impurities: suspended solids, bacteria, parasites, viruses, organic matter, heavy metals, and chlorine. Breakdown and other problems with water treatment systems sometimes lead to incomplete removal of bacteria and viruses. In other countries, there are deadly consequences associated with exposure to contaminated water, as some of them have increasing population densities, increasingly scarce water resources, and no water treatment utilities. It is common for sources of drinking water to be in close proximity to human and animal waste, such that microbiological contamination is a major health concern. As a result of waterborne microbiological contamination, an estimated six million people die each year, half of which are children under 5 years of age.
In 1987, the U.S. Environmental Protection Agency (EPA) introduced the xe2x80x9cGuide Standard and Protocol for Testing Microbiological Water Purifiersxe2x80x9d. The protocol establishes minimum requirements regarding the performance of drinking water treatment systems that are designed to reduce specific health related contaminants in public or private water supplies. The requirements are that the effluent from a water supply source exhibits 99.99% (or equivalently, 4 log) removal of viruses and 99.9999% (or equivalently, 6 log) removal of bacteria against a challenge. Under the EPA protocol, in the case of viruses, the influent concentration should be 1xc3x97107 viruses per liter, and in the case of bacteria, the influent concentration should be 1xc3x97108 bacteria per liter. Because of the prevalence of Escherichia coli (E. coli, bacterium) in water supplies, and the risks associated with its consumption, this microorganism is used as the bacterium in the majority of studies. Similarly, the MS-2 bacteriophage (or simply, MS-2 phage) is typically used as the representative microorganism for virus removal because its size and shape (i.e., about 26 nm and icosahedral) are similar to many viruses. Thus, a filter""s ability to remove MS-2 bacteriophage demonstrates its ability to remove other viruses.
Due to these requirements and a general interest in improving the quality of potable water, there is a continuing desire to provide low cost filter materials and filters which are capable of removing bacteria and/or viruses from a fluid. Further, there is a continuing desire to provide such filter materials in the form of fibers in order to reduce the pressure differential needed to pass a fluid through the filter material.
Filters and filter materials for removing microorganisms from a fluid are provided along with processes for using the same. In one embodiment of the present invention, the filter includes a housing having an inlet and an outlet and a filter material disposed within the housing, wherein the filter material is formed at least in part from a plurality of filter particles having an activated lignosulfonate coating. A preferred lignosulfonate is ammonium lignosulfonate and exemplary filter particles can be provided in the form of glass fibers or ceramic fibers.